January 17, 2012: As Congress returns from its winter recess, protesters aligned with the Occupy Wall Street movement demonstrate on Capitol Hill in Washington to decry the influence of corporate money in politics.

WASHINGTON – An apparent smoke bomb was thrown over the fence of the White House as hundreds of Occupy protesters massed outside the gates.

The crowds were dispersed Tuesday night, and U.S. Secret Service spokesman George Ogilvie says there were no arrests in the incident.

The Obamas were at dinner celebrating Michelle Obama's birthday, but they have since returned to the White House without difficulty.

The tense scene outside the White House follows an earlier protest on the West Lawn of the Capitol, in which several hundred protesters affiliated with the Occupy Wall Street movement decried the influence of corporate money in politics and voice myriad other grievances.

Organizers had touted the rally, known as Occupy Congress, as the largest national gathering of Occupy protesters to date and secured a permit that would have allowed up to 10,000 people to participate. By mid-afternoon, the protest appeared to have fallen far short of those goals.

Still, participants said they were optimistic about the strength of the Occupy movement, which began in September when protesters pitched tents in a lower Manhattan park. The movement has since spread to dozens of cities, including Washington. While many cities have moved to evict the protesters, the National Park Service has allowed encampments to remain in two public squares near the White House.

"I'm encouraged," said Jon Wynn, 63, of North Carolina, who traveled to Washington to attend the protest and visit friends. "There's energy here, even if there's not a whole lot of people."

While the rally was mostly peaceful, there were some scuffles between police and protesters along walkways leading to the Capitol. By mid-afternoon Tuesday, four people had been arrested -- U.S. Capitol Police said -- one for allegedly assaulting a police officer and three accused of crossing a police line.